1. Field of the Invention
The present invention relates in general to a calibration system of an industrial robot, and more particularly to an improved calibration system for compensation of arm length variation of the industrial robot in which the arm length variation caused by operational peripheral temperature change is detected by a noncontact sensor unit and automatically compensated in order to make the varied position of the tool center point mounted on a distal end of a robot hand to precisely return to its preset reference position with respect to a workpiece.
2. Description of the Prior Art
Conventionally, there occasionally occurs arm length variation of a known industrial robot because of peripheral temperature change of the automatic production line equipped with the industrial robots, as a result, a tool center point mounted on a distal end of a robot hand of the robot arm is deviated from the preset reference position thereof with respect to a workpiece to be machined. In this respect, a problem of the known industrial robot is resided in that the operational accuracy of the robot, which is taken a serious view of the automatic production using the industrial robots, is necessarily reduced and this causes quality of the result product of the automatic production to be deteriorated.
In result, in order to repeatedly carry out the automatic workpiece machining, using the industrial robots, with provision of such a desired operational accuracy, it is required to detect the arm length variation of the industrial robot caused by the peripheral temperature change and compensate the arm length variation in order to make the tool center point of the robot hand to return to its preset reference position from the detected varied position. In order to accomplish the aforementioned object, two known methods have been typically used. Otherwise stated, the automatic production line equipped with industrial robots is installed in a constant temperature room wherein the operational temperature can be maintained constant or the arm length variation caused by the operational peripheral temperature change is detected by a sensor and forcedly compensated in order to cause the varied position of the tool center point of the robot hand to be returned to the preset reference position with respect to the workpiece.
However, in the case of use of a part of the industrial robot as such a sensor for detecting the arm length variation, it may be impossible to install the constant temperature room for the industrial robots or to compensate the robot arm length variation by means of a conventional camera system for sensing and compensating the arm length variation. In this respect, the known methods for overcoming the robot arm length variation due to the peripheral temperature variation have a problem in that they, irrespective of their types, can not accomplish the compensation of arm length variation of the robot in such a case, or the case of use of a part of the robot as the arm length variation sensor.